The disclosed embodiments of the present invention relate to detecting capacitance values of a touch panel, and more particularly, to a method and apparatus for using oscillation signals with different phases to detect capacitance values (e.g., mutual capacitance values) at capacitive sensing nodes of a touch panel.
Touch panel devices are now widely used in a variety of applications to act as user interfaces. In general, a touch panel device may include a touch panel and a touch controller. Regarding certain applications, capacitive touch panels (e.g., mutual-capacitance touch panels) may be used. Thus, the touch controller generates a driving input to the capacitive touch panel, receives a sensing output generated from the capacitive touch panel, and refers to the sensing output to determine mutual capacitance values for detecting a touch event.
Regarding some touch panel systems, multiple drive lines (i.e., row traces) of the mutual-capacitance touch panel are stimulated simultaneously to generate composite sensing outputs at the sense lines (i.e., column traces). However, different drive lines may introduce different phase delays in the sensing outputs, which results in the complexity in determining the mutual capacitance values corresponding to intersections (i.e., crossover points) of drive lines and sense lines. Besides, as the phase delay would change along with the ambient temperature variation, the phase delay measurement and compensation may be inaccurate, thus degrading the overall touch-controlled system performance.
In view of the foregoing, there is a need for an innovative design which can correctly and efficiently determine capacitance values corresponding to intersections (i.e., crossover points) of drive lines and sense lines on a multi-stimulus touch panel.